The present invention relates to an apparatus for cooling elongated products during their passage through the apparatus.
Apparatus of this type essentially comprises an elongated tube flown through by a cooling liquid, usually water, and through which passes also the elongated product to be cooled.
The tube is equipped at one of its ends with a cooling fluid supplying head and at its opposite end with a separator used to separate at the outlet end of the tube the product passing therethrough from the cooling fluid.
Such apparatus is especially used in the field of metallurgy and more precisely for special thermic treatment of elongated products coming from a hot rolling mill. However, such apparatus may evidently be used also for other applications.
Despite the efficiency of such known apparatus the homogeneity of the treatment of the product is nevertheless not always obtained due to the form of the product to be cooled and the speed with which it is passed through the apparatus.
It has been especially ascertained that the uniformity of the thermic treatment is essentially better in the case of cooling elongated round bars provided with a helical groove than round bars having a smooth cylindrical outer surface. Questioning the cause of this difference, the inventors have visualized the possibility that this difference results from contact of the product passing through the tube with the interior surface of the latter.
It will be understood that under these conditions the cooling liquid cannot any longer uniformly cool the product over its whole circumference.
Experiments carried out by the inventors have confirmed this initial hypothesis and experience has effectively shown that elongated products such as steel bars present due to their weight and the relatively low speed at which they pass through the apparatus in the interior of the tube a sag or bent large enough so that the product will partially abut against the bottom surface of the tube. The reason why bars provided at the outer surface with a helical groove are better treated than bars having a smooth cylindrical outer surface seems therefore clear since the grooves permit the passage of the cooling liquid beneath the portion of the bar which abuts against the inner surface of the tube.
In order to prevent contact of any portion of the bar with the inner surface of the tube a cooling apparatus has already been proposed in which a plurality of guide funnels are provided in the tube (French Pat. No. 1,569,259), but this apparatus does not assure a uniform cooling of the product and it is necessary to provide a plurality of cooling fluid injection means over the length of the apparatus. Apparatus had likewise already been proposed with guidance elements of more complex form which permit to create a turbulence of the cooling fluid (German Pat. No. 2,556,383) or provided with elliptic sections which are rotatable about the axis of the tube (U.S. Pat. No. 4,126,544).
All these known apparatus can be used only with a great supply of the cooling fluid assuring a high speed of the cooling fluid through the apparatus due to great pressure loss resulting from the guide elements.